Individuals are susceptible to radiation and chemotherapy-induced cancer. Patients who develop one malignancy and are treated with radiotherapy and/or chemotherapy have the risk of the development, many years later, of a second malignant neoplasm which may be attributable to the carcinogenic effects of treatment. The prototypical malignancy in which improved survival is linked to the development of second malignant neoplasms is Hodgkin's disease. With the trowing popularity of combined modality therapy for childhood brain tumors, this class of tumors is joining Hodgkin's disease in being associated with therapy -induced tumors. In this protocol, we seek to determine the frequency of chromosome aberrations in peripheral blood lymphocytes specifically associated with iatrogenic acute myelogenous leukemia using chromosome painting techniques following the radiation therapy and/or chemotherapy used in the treatment of Hodgkin's disease and childhood brain tumors. We are also using blood samples from these patients to study toxicological response to carcinogenic exposure and gene rearrangements associated with deregulation of a growth promoting oncogenes. Through these techniques, we hope to develop predictive assays for treatment-induced second malignant neoplasms which may lead to an improved understanding of this complication of cancer treatment and, perhaps, preventive and therapeutic strategies.